Biexponential Analysis of Diffusion Related Signal Decay in Normal Human Cortical and Deep Gray Matter

摘要

Diffusion imaging with high-b factors, high spatial resolution, and cerebro-spinal fluid signal suppression was performed in order characterize the biexponential nature of the diffusion-related signal decay with b-factor in normal cortical gray and deep gray matter. Integration of inversion pulses with a line scan diffusion imaging sequence resulted in 91% cerebro-spinal fluid signal suppression, permitting accurate measurement of the fast diffusion coefficient in cortical gray matter (1.142±0.106 μm²/ms) and revealing a marked similarity with that found in frontal white matter (1.155±0.046 μm²/ms). The reversal of contrast between gray and white matter at low vs high b-factors is shown to be due to a significantly faster slow diffusion coefficient in cortical gray matter (0.338±0.027 μm²/ms) than in frontal white matter (0.125±0.014 μm²/ms). The same characteristic diffusion differences between gray matter and white matter are observed in other brain tissue structures. The relative component size showed not significant differences among all tissues investigated. Cellular architecture in GM and WM are fundamentally different and may explain the two to three-fold higher slow diffusion coefficient in GM.